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Data are sparse regarding how physicians use coronary risk information for prescribing decisions.
We presented primary care physicians affiliated with an academic center with five primary prevention scenarios, and surveyed their responses after presented with patient risk factors, then with 10-year estimated coronary disease risk, and then with 10-year and lifetime risk estimates. We asked about aspirin prescribing, lipid testing, and lipid-lowering drug prescribing.
Of 202 surveyed, 99 (49 %) responded. Physicians made guideline-concordant aspirin decisions 51 to 91% of the time using risk factor information alone. Providing 10-year risk estimates increased concordant aspirin prescribing when 10-year coronary risk was moderately high (15 percent) and decreased guideline-discordant prescribing when 10-year risk was low in 2 of 4 cases. Providing lifetime risk sometimes increased guideline-discordant aspirin prescribing. Physicians selected guideline-concordant thresholds for initiating lipid-lowering drugs 44 to 75% of the time using risk factor information alone. Selecting too low or too high LDL thresholds were both common. Ten-year risk information improved concordance when 10-year risk was moderately high. Providing lifetime risk increased willingness to initiate pharmacotherapy at LDL levels lower than recommended by guidelines when 10-year risk was low but lifetime risk was high.
Providing 10-year coronary risk improved some hypothetical aspirin prescribing decisions and improved lipid management when short-term risk was moderately high. High lifetime risk sometimes led to more intensive prescription of aspirin or lipid-lowering medication. This outcome suggests that, to maximize the benefits of risk calculating tools, specific guideline recommendations should be provided along with risk estimates.
Current guidelines for the primary prevention of cardiovascular disease advocate using information from multiple risk factors to guide decision making.1-5 Patients with higher estimated risk generally should receive more intensive risk reduction interventions such as aspirin or pharmacotherapy to lower cholesterol. Physicians have difficulty accurately estimating cardiovascular risk when provided with patient risk factor information alone.6 Multivariable risk estimation methods, such as the Framingham Risk Score,7 or the European SCORE,8 produce estimates of risk over the next 10 years. These tools require that clinicians either perform a manual risk estimation process using tables or enter risk variables into a computer application to calculate risk.9 Providing this kind of risk information to physicians or physicians and patients, either manually or using automated methods, can improve the appropriate use of preventive therapies in some cases.10-15 Calculating cardiovascular risk routinely also could improve aspirin prescribing for primary prevention. Though major guidelines differ to some degree with respect to aspirin prescribing for primary prevention, all include the use of some form of risk assessment to guide therapeutic decision making.2,3,5 Prior work has identified aspirin underuse by some patients with increased risk and potentially inappropriate use by some with low risk.16, 17,18 However, provision of short-term cardiovascular risk estimates has not demonstrated a strong effect in most experimental studies. Important treatment gaps remain, and guidelines still are not followed for significant portions of eligible patients.10-15, 19, 20
Recently, methods have been developed to estimate an individual’s cardiovascular risk over their remaining lifetime.21, 22 Knowledge of lifetime risk could help inform physicians and patients as they make decisions about therapies to reduce cardiovascular risk. Physicians who are inclined to not treat patients whose cholesterol is above a guideline goal might make different decisions for patients with high lifetime risk for cardiovascular disease. But, this information could also lead physicians to prescribe treatments inappropriately – such as recommending aspirin to a patient with a low short-term risk of cardiovascular disease, in whom the risk for bleeding complications would exceed the expected benefit in cardiovascular risk reduction.
We sought to examine whether and how providing calculated 10-year risk estimates influenced preventive cardiology decision making and to determine the additional impact of adding lifetime risk information.
We surveyed all of the 202 primary care physicians who had an academic affiliation with Northwestern University’s Feinberg School of Medicine and who cared for adults in the fall of 2008. The majority, 82.2 %, were affiliated clinical faculty whose predominant academic activity is office-based teaching of medical students or residents, and the remainder were members of the full-time medical school faculty and were internists practicing in the outpatient setting. The university’s Institutional Review Board approved the study. We mailed physicians a survey with a two dollar bill and also contacted them by email up to 3 times. Physicians could respond using either the mail or email version of the survey. The survey presented specific clinical scenarios (described in Table 1) in the following order: first with hypothetical patients’ coronary heart disease risk factor information alone, then with additional information on their estimated 10-year coronary disease risk (cardiac death or nonfatal myocardial infarction) based on continuous models from the Framingham Study,7 and then with both 10-year and lifetime coronary disease risk estimates. Lifetime risk estimates were derived from the Cardiovascular Lifetime Risk Pooling Project, an ongoing study using pooled data from 17 major longitudinal epidemiologic cohort studies in the U.S. that takes into account both the risk of developing coronary disease as well as the risk of dying from other causes using methods similar to those employed previously in single cohort studies.21, 22
Physicians were instructed to complete the survey with only the information provided at each step and not to skip ahead or go back to previously answered questions (though there was nothing to prohibit them from answering questions out of order). For each case, we asked physicians 1) whether they would prescribe low dose aspirin, 2) when they would repeat lipid testing (5 years, 1 year, 6 months, 6 weeks, or start therapy without retesting), and 3) at what level would the LDL cholesterol need to remain above on retesting (with confirmation by repeating a second time if necessary) for them to prescribe cholesterol-lowering drug therapy (190, 160, 130, 100 or 70 mg/dl). We asked physicians to respond to identical multiple choice questions three times per patient scenario: based on risk factor data alone, after providing the 10-year risk estimate, and after providing both 10-year and lifetime risk estimates. In all cases, there was a family history of one parent with a myocardial infarction after age 70 and no medical problems that would represent a contraindication to aspirin or cholesterol-lowering medication.
We assessed whether prescribing thresholds were concordant or discordant with contemporary guidelines. For aspirin prescribing, we considered the response to be concordant if aspirin was prescribed in the case where 10-year coronary risk was 15% and not prescribed in cases with 10-year risk of 2 to 4%.2 For lipid monitoring and prescribing, we considered responses to be guideline concordant if responses were consistent with the National Cholesterol Education Program Adult Treatment Panel (NCEP ATP) III recommendation1 or the optional thresholds described in 2004.4
For aspirin prescribing decisions, we used McNemar’s test to determine the agreement of responses before and after the addition of additional pieces of risk information among physicians who answered all three questions within a single case. For cholesterol monitoring or thresholds for drug prescribing, we used Bowker’s test of symmetry because there were more than two possible responses.23 We performed exploratory analyses to determine whether the survey results varied by physician sex, full-time medical school faculty compared to affiliated clinical faculty, hours of direct patient care per week (≤ 20 hours per week vs. >20 hours per week), years since training completed (<10 vs. ≥ 10), and whether or not physicians reported using a risk calculating tool for aspirin prescribing or cholesterol-lowering drug treatment decisions (never/rarely vs. sometimes or more often) using Fisher’s exact test. We used SAS version 9.2 (SAS Institute, Cary, NC) for all analyses.
One hundred four of 202 physicians returned surveys, of which 99 contained usable data (49% response rate). Among responders, 28% were full-time medical school faculty (compared to 8% of non-responders; P <0.001), and 59% were male (compared to 49% for non-responders; P=0.16). All respondents were practicing primary care internists. The number who responded to all clinical questions within each of the three sets of risk information (risk factors only, risk factors with 10-year risk, and risk factors with 10-year and lifetime risk estimates) ranged from 90 to 95. Respondents’ characteristics are provided in Table 2. Thirty-seven percent of respondents reported that they rarely or never used a risk calculating tool when making prescribing decisions for the primary prevention of cardiovascular disease.
Physicians made guideline-concordant aspirin prescribing decisions 51 to 91 % of the time when provided risk factor information alone. The provision of 10-year risk information significantly improved guideline-concordant aspirin prescribing when 10-year risk was moderately-high (the 10-year risk of cardiac death or nonfatal myocardial infarction was 15 %, Table 3, Case 2). In two of the four clinical scenarios where 10-year risk was low, explicitly providing physicians with the 10-year risk reduced aspirin prescribing that was not guideline concordant (Cases 3 and 4). Providing lifetime risk information increased aspirin prescribing in all three scenarios where 10-year risk was low and lifetime risk was moderate or high (Table 3, Cases 1, 4 and 5). Such prescription would not be concordant with contemporary guideline recommendations based on 10-year risk estimates.2,3
For the two cases in which the LDL cholesterol was not at the NCEP ATP III goal (Cases 1 and 2), physicians often selected a wait time longer than that recommended by the guideline before repeating lipid testing (NCEP ATP III recommends instituting therapeutic lifestyle change and repeating testing in 6 weeks) (Table 4). Providing lifetime risk information increased immediate prescribing without repeat testing from 2% to 12% in the case of a patient who was not at goal and had low 10-year and high lifetime risk (Case 1)—a decision that is not concordant with guideline recommendations. Providing 10-year risk information in Case 2, in which both 10-year and lifetime risk were high, increased immediate prescribing without repeat testing—a decision concordant with the optional 2004 guideline.4
For cases in which LDL cholesterol was at goal (Cases 3, 4 and 5), physicians rarely waited the 5 years permitted in the NCEP ATP III guideline before retesting (Table 4). Neither provision of 10-year risk estimates nor provision of lifetime risk estimates significantly changed physician recommendations for the timing of retesting.
Physicians selected LDL cholesterol thresholds for initiating lipid-lowering drugs consistent with the NCEP ATP III or the optional 2004 guideline 44 to 75% of the time with risk factor information alone (Table 5).
For the case with low 10-year and high lifetime risk (Case 1), physicians’ LDL treatment thresholds were the same as the ATP III guideline 44% of the time, whereas similar numbers of physicians selected higher or lower thresholds. Providing the lifetime risk estimate led more physicians to select an LDL threshold for drug treatment that was lower than the guidelines currently recommend (Table 5).
When both 10-year and lifetime risk were elevated (Case 2), 32% of physicians selected an LDL threshold for drug prescribing of 160 mg/dl or greater when presented with just risk factor information — responses that are above guideline recommendations. Addition of 10-year risk or 10-year and lifetime risk information led to an increase in guideline-concordant responses (Table 5).
When 10-year risk was low and lifetime risk was low or moderate (Cases 3, 4 and 5), physicians selected an LDL threshold for drug therapy below the optional 2004 guideline recommendation of ≥160 mg/dl after therapeutic lifestyle change 16 to 46% of the time. Neither provision of 10-year risk estimates nor provision of lifetime risk estimates significantly changed prescribing thresholds in these cases (Table 5).
In secondary analyses, several physician characteristics were associated with guideline-concordant responses. When provided risk factor information alone, women physicians were more likely than men to prescribe aspirin when the 10-year risk was moderately-high, Case 2, (94% for women physicians vs. 71% for men, p=0.007), and this difference was reduced by the provision of 10-year risk information (97% for women and 89%) and was no longer statistically significant.
Physicians with ≤ 20 hours of direct patient care per week, those who were full-time medical school faculty, and those with less than 10 years since completion of their training were more likely in some cases to provide NCEP ATP III guideline concordant responses for when to perform repeat lipid testing among patients who were at their LDL-cholesterol goal . Namely they were more likely to report they would wait 5 years to retest lipids, compared to physicians with >20 hours per week of patient care, affiliated clinical faculty, and those with 10 or more years since completing training, respectively.
Physicians who reported they rarely or never used a cardiovascular risk calculating tool to aid with prescribing decisions were significantly less likely to select an LDL-cholesterol threshold for prescribing cholesterol-lowering therapy concordant with contemporary guidelines for a low short-term, moderate lifetime risk woman with an LDL-cholesterol of 158 mg/dl (Case 4). Providing additional risk information had little impact on this association.
Practicing primary care physicians — many of whom do not routinely use a risk-estimation tool for prescribing decisions — frequently made preventive cardiology treatment choices inconsistent with major prevention guidelines when provided with patient risk factor data alone. Physicians often recommended aspirin in cases where short-term coronary risk was low, yet 20% did not recommend aspirin to a male patient with a 10-year coronary risk of 15%. They recommended repeat lipid testing less promptly than recommended for individuals not at their guideline goal for LDL cholesterol and tested more frequently than recommended for patients at goal at the time of screening. It was not uncommon for physicians to select LDL thresholds for drug prescribing that were higher or lower than guideline-recommended thresholds. These findings are consistent with prior studies examining adherence to or agreement with cardiovascular disease prevention guidelines for lipid management,6, 24, 25 hypertension treatment,6, 26, 27 or aspirin prescribing,6 which have shown that considerable numbers of practicing physicians choose management recommendations that are inconsistent with major contemporary guidelines.
Inaccurate appraisal of cardiovascular risk may be an important explanatory factor leading to guideline-discordant choices.6,28 Providing estimates of 10-year coronary risk using the method derived from the Framingham Heart Study led to several important changes in physicians’ choices. Physicians made aspirin prescribing decisions more concordant with evidence-based guidelines; they prescribed aspirin more often in the case where short-term risk was moderately-high and they reduced prescribing when short-term risk was low in some cases. Providing 10-year risk information also increased the proportion of physicians who made guideline-concordant cholesterol management choices for an individual with multiple risk factors and moderately-high 10-year risk (≥10% risk of cardiac death or nonfatal myocardial infarction). For the most part though, respondents who provided guideline-discordant answers when provided risk factor data alone did not change their response when given the 10-year coronary risk estimate—the technique recommended by contemporary U.S. guidelines to inform clinical decision making.1-4 These findings suggest that even when physicians obtain a 10-year risk estimate, through use of a risk table or the National Heart Lung and Blood Institutes’ online risk calculator,29 this step alone may not result in appropriate clinical decision making. The results also are consistent with the modest or negative results of clinical studies aimed at increasing physicians’ use of short-term cardiovascular risk estimates for clinical decision making.11, 15, 19, 20
Recent prevention guidelines advise clinicians to take patients’ lifetime risk for coronary disease into consideration.1, 3 Individuals with low short-term but high lifetime risk, who represent a substantial proportion of the population under 50 years of age,30 should attempt intensive lifestyle modifications and consider using lipid-lowering medication when LDL cholesterol remains high.1 Providing lifetime risk estimates for coronary disease to physicians generally did not alter their prescribing decisions substantially with regard to aspirin. It did, however, lead physicians to prescribe aspirin more often in cases where the lifetime risk was 26 to 43% but the 10-year risk was low. Such a decision would be inconsistent with current guideline recommendations based on 10-year risk estimates. This finding suggests that specific education may be needed to improve physicians’ awareness that aspirin prescribing should be based on a determination that the potential short-term benefits clearly exceed a patient’s risks of treatment. Making lifetime risk information available in addition to 10-year risk did alter physicians’ cholesterol monitoring and drug therapy prescribing decisions in one case (Case 1, a man with low short-term, high-lifetime risk and LDL cholesterol of 135 mg/dl). However, instead of improving guideline concordance by increasing the number of physicians who would initiate lifestyle changes and retest in six weeks, providing lifetime risk led more physicians to recommend immediate drug treatment–at a lower LDL threshold than is currently recommended. Whereas clinical trial data suggest that relative risk reductions with statin therapy are similar over 5 years regardless of baseline LDL-cholesterol level,31 the absolute level of risk determines the number needed to treat to prevent an event and substantially influences short-term cost-effectiveness. Data are sparse regarding the long-term effectiveness and cost-effectiveness of statin therapy for individuals with lower short-term but high lifetime risks for coronary heart disease.
Our findings could inform the development of intervention strategies aimed at improving preventive cardiology care for the prescribing of aspirin or cholesterol-lowering medication. Many physicians in our study reported a lack of routine use of a risk calculating tool for preventive cardiology decision making. Automating the risk assessment process using computerized decision support within electronic health records offers the potential to make cardiac risk information more readily available to clinicians.32,33 However, since guideline-discordant responses were common even when short-term or lifetime risk estimates were provided, risk estimation tools intended to increase guideline-recommended treatments should also provide recommendations for specific clinical actions. One particularly successful study of computerized decision support aimed at improving preventive cardiology practice for lipid management generated cardiovascular risk assessments from data within electronic health records and provided clinicians with both an estimate of risk and specific guideline-based recommendations. Among the patients served by physicians receiving automated alerts, 66 % of those requiring treatment received it, compared to 36% of the corresponding control group.10
The results of this study should be viewed with several limitations in mind. Respondents included proportionally more full-time medical school faculty than the overall population. There may also have been other unmeasured differences between responders and non-responders (e.g. physicians more interested or familiar with prevention guidelines may have been more likely to respond). These differences may have led to a greater proportion of guideline-concordant responses than had the entire population responded. We surveyed practicing internists from multiple practices, but all were affiliated with a single institution in one city. We do not know how generalizable these findings are to other groups of practicing primary care physicians. The size of the study was fairly small and there may have been additional significant findings if more physicians had been surveyed. The way in which the cases were presented in order may have influenced how physicians made their choices. Physicians may have been less likely to use risk estimates to inform their hypothetical decision making if they felt committed to the original choice they made using risk factor data alone. It is not known whether providing these forms of risk estimates in actual practice would influence clinical decision making in the same way.
In summary, providing 10-year coronary risk information to physicians improved hypothetical prescribing decisions for aspirin, but lifetime risk information led physicians to over treat with aspirin for primary prevention, compared with contemporary guideline recommendations. Guideline-discordant choices for cholesterol management were fairly common and were usually not influenced by provision of risk information. Providing estimated 10-year risk improved concordance with current cholesterol management recommendations when short term risk was moderately high. Providing lifetime risk estimates may lead some physicians to prescribe lipid-lowering medications more intensively and in a manner inconsistent with contemporary guidelines based solely on short-term level. These findings suggest that, to maximize the benefits of risk estimation tools, they should be coupled with clinical decision support that provides specific guideline recommendations along with risk assessment.
This work was supported by the Mentored Clinical Scientist Development award 1 K08 HS015647-01, Agency for Healthcare Research and Quality, to Dr. Persell. We would like to thank Drs. Heather L. Heiman and Toshiko Uchida for their valuable feedback during the development of the survey instrument. We would also like to thank the REACH Network for coordinating data collection. We are grateful to all the physicians who completed the survey. Dr Lloyd-Jones and the Cardiovascular Lifetime Risk Pooling Project were supported by R21 HL085375 from the National Heart, Lung, and Blood Institute. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. Dr. Persell had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.